In general, a liquid crystal cell harboring liquid crystal and a polarizing plate are required to prepare a liquid crystal display device. To attach these components together, a proper adhesive layer is required. To improve the function of a liquid crystal display device, a retardation plate, a wide-viewing angle plate, or a brightness-enhancing film can be additionally laminated onto a polarizing plate.
The general structure of a liquid crystal display device comprises a liquid crystal layer arranged evenly; a multiple structure polarizing plate, wherein a liquid crystal cell comprising a glass plate containing a transparent electrode layer or a plastic board is coated with an adhesive layer; a retardation plate; and a supplementary functional film.
Regarding an adhesive used for the attachment of a polarizing plate, Japanese Laid-Open Patent Publication No. 3022993 describes an acrylic adhesive composition containing a silane compound having an epoxy group, and Japanese Laid-Open Patent Publication No. Hei 7-331204 describes an adhesive composition containing a silane compound having a hydrocarbon group. However, the silane compound containing adhesive cannot provide the satisfactory adhesive strength required for application to a substrate and a polarizing plate in practical use, and has the problems of leaving the adhesive behind after removal and an excessive increase of adhesive strength under high humidity and high temperature conditions.
Japanese Laid-Open Patent Publication No. Hei 8-104855 describes an adhesive composition containing a silane compound with a β-keto ester group and an alkoxy group on its acrylic polymer which exhibits the proper adhesive strength to attach a polarizing plate to the surface of a substrate, and enables removal without leaving the adhesive behind or damaging the substrate.